Process of refining a petroleum oil containing naphthenic acids



Patented July 15, 1947 PROCESS OF REFINING A PETROLEUM OIL CONTAINING NAPHTHENIC ACIDS Mack C. Fuqua and John B. Lovell, Baton Rouge, La., assignors to Standard Oil Development Company, a corporation of Delaware Application September 20, 1944, Serial No. 555,026

12 Claims.

an acid-free oil layer and a solvent extract layer containing the salt of the naphthenic or other acids removed from the oil, after which this extract layer is treated with an acidic gas such as carbon dioxide in order to liberate the free organic acids, and in order to convert the organic base into the carbonate form. The freed acids are then readily separated from the solvent containing the organic base carbonate, and the carbon dioxide is readily driven off by distillation in order to regenerate the organic base dissolvedin the solvent which may then be recycled.

Although the invention may be carried out by batch, if desired, it is preferable from a practical commercial point of view to operate by continuous countercurrent solvent extraction, followed by continuou treatment and separation in the various phases of the invention as mentioned above. v

In the past, considerable work has been done in an'efiort to remove naphthenic acids from certain crudes, both for the recovery of the naphthenic acid and to free the variousdistillate cuts of the crude from acidic material. The removal of these acids by alcoholic KOH or aqueous alkali, followed by acidification and extraction with a low-boiling distillate has not proved very successful due to the formation of emulsions.

By the present invention, a very high percent of the total naphthenic acid content of the crude petroleum can be removed. Several advantages result from this invention. One is that the substantially complete removal of the naphthenic acids from the crude oil prior to any distillation enables the obtaining of acid-free distillates from the original crude distillation without the injection of any neutralizing substance, and prevents any corrosion or coking of furnace tubes during distillation. Another advantage is that the total naphthenic acids are obtained and these may then be separated by subsequent distillation into fractions of any desired boiling range; whereas if I the crude oil is first subjected to distillation prior to acid removal then each separate distillate must be subjected to acid removal treatment if all of the naphthenic acids are to be recovered and if each distillate is to be produced in an acidfree condition. A still further advantage of this invention is that it permits regeneration of the organic base and recovery of the solvent, thus enabling the recycling of both of these agents.

The invention may be applied to various types of crude oils such as parafiinic, naphthenic, asphaltic, or mixed base crude petroleum oils, although the invention is intended to apply most particularly to crudes having a naturally high content of. naphthenic or other organic acids,

such as coastal crude, specifically White Castle,

Refugio, New Iberia, ,Webster, Friendsward, Thompson, Bayou Blue, Bayou Bouillon, Heavy Black Bayou, Charenton, Lake Washington, and

Potash.

The organic base to be used should be one sufficiently basic to form organic salts with the naphthenic acids in the oil, and yet should have good solubility characteristics in relation to the solvent or contact agent and when dissolved therein to the oil being treated. The watersoluble and alcohol-soluble amines constitute a suitable class of bases, and the amino-alcohols. or otherwise called the hydroxyamines, are preferred. Good results have been obtained with mono-ethanol amine, di-ethanol amine and triethanol amine. Other specific amines which can be used include: methyl amine, ethyl amine, n-

and isopropyl amine, n-butyl amine, sec-butyl amine, ter-butyl amine, propanol amine,isopropanol amine, butanol amine, sec-butanolamine, and ter-b'utanol amine.

The contact agent to be used should be an organicliquid capable of acting first as a mutual solvent for the amines and the naphthenic acid salts; and secondly, it must be capable of serving as solvent medium for the carbonate salts of the naphthenic acids resulting from the CO2 treatment, and yet be sufficiently insoluble in naphthenic acids per se that itssolution with regenerated amine will separate readily from the liberated naphthenic acids. A suitable class of compounds for filling these requirements is the class of lower aliphatic alcohols. Isopropyl alcohol has been found particularly suitable but others may be used such as ethyl alcohol, methyl alcohol, normal propyl alcohol, or even some of the butyl alcohols. Other low molecular weight oxygen-containing organic solvents may be used, such as acetone, glycerin, methyl ethyl ketonc, ethylene glycol, Water-soluble esters, as ethyl alcohol.

3 acetate, ethyl propylate and isopropylate, or any water-soluble, oll--insoluble solvent.

The proportions of organic base and contact agent in the solvent to be used may, of course,

vary within fairly broad ranges depending upon the concentration of acids in the crude oil being treated, and On the amount of base used to extract the oil, and on the water-solventiextract) layer. This quantity may best be regulated by pH measurements. I

Although the separation of the liberated naphthenic acids from the solvent solution of hydroxyamino-carbonates usually takes place readily upon settling, such separation may be initiated if necessary, or in any event accelerated, by cooling, or heating, by adding additional solvent, or if necessary by adding some precipitating solvent such as water.

The final step of heating the solvent solution of hydroxyamino-carbonates to regenerate the hydroxyamine by liberation of carbon dioxide may be carried out in an ordinary tower still equipped with steam heating coils at suitable elevations, so that regenerated solvent may be withdrawn by gravity and liberated carbon dioxide given ofi at the top may be recycled into the converter.

The invention will be better understood from a consideration of the attached drawing in conjunction with the following description which, without intending to limit the invention to the specific materials employed nor the precise equipment used, will illustrate the application of the invention to the continuous countercurrent sol-- vent extraction of a crude petroleum oil with mono-ethanol amine in the presence of isopropyl Referring, to the drawing, a crude petroleum oil is fed through inlet line I into extractor 2 in the lower portion thereof and it rises countercurrently to a descending flow of solvent entering the upper portion of the tower through line' 3. The solvent liquid flowing in line 8 is composed of isopropyl alcohol which may be fed in through line 4, and ethanol amine which may be fed in through line 5 together with recycle solvent flowing through line 6, as will be explained more fully later.

As the oil rises through extractor 2 the naphthenic acids and other organic acids therein are gradually and substantially completely removed so that when the oil reaches the top of the extractor it is substantially acid-free and flows out through discharge line I, after which it may be subjected to distillation or various refining steps as desired, without the necessity of adding any corrosion-preventing agent. In the meantime, the solvent comprising isopropyl alcohol containing ethanol amine dissolved therein descends through the extractor 2 and removes the naphthenic and other acids by forming ethanol amine salts such as ethanol amine naphthenates, etc. which remain dissolved in the isopropyl a1- cohol so that this resulting extract is withdrawn 4 from the extractor by gravity by line 8 and is passed into through line 9 into the upper portion of a converter l0 which may suitably be a vertical tower into which carbon dioxide is blown in near the bottom through line ll, any unabe sorbed gases being vented through line 12 at the top, from which they may or may not be recov ered and recycled, while the liquid phase now consisting of a mixture of isopropyl alcohol containing ethanol amine carbonate dissolved therein and the oily liberated naphthenic acids which are insoluble in the alcohol solution, is withdrawn by gravity from the base of the converter It by discharge line- I3 and passed through line I! into the separator 15 at or about the middle.

thereof, wherein the lighter oily naphthenic acids separate and rise to form an upper layer which is withdrawn through line It, while the alcohol solution of ethanol amine carbonate settles as a lower layer and is withdrawn from the bottom of the separator l5 and passed through line I! into the still l8 which may be a vertical tower provided with suitable steam heating coils l9 or other suitable heating means, to drive oi! carbon dioxide from the top of the still ll through line 20, for recycling if desired through line 2|, while the residual isopropyl alcohol solution of regenerated ethanol amine is withdrawn by gravity from the bottom of still l8 through discharge line 22 for recycling through lines 2'3,

. 6 and 3 into extractor 2.

Laboratory extraction of a coastal crude (White Castle) with a 1.30 neutralization number using 3% by volume 'of mono-ethanol amine in the presence of by volume of isopropyl alcohol gave 94% removal of the naphthenic acid in the crude. Upon distillation of the amine-alcohol layer a 75% recovery of alcohol was obtained and a practically complete recovery of the amine.

Subsequent extractions with various concentrations of amines, and using ethyl alcohol as well as isopropyl alcohol as a contact agent, gave comparable naphthenic acid removal.

It is understood of course that the naphthenic acid fraction recovered by this invention, as for instance, through line It in the drawing, may be subjected if desired to any further separating or purification steps, such as by distillation, additional extractions, or acid treating to give desired purity.

It is not intended that this invention be limited to the specific materials for equipment which have been recited merely for the sake of illustration, but only by the appended claims in which it is intended to claim all novelty inherent in the invention as well as all modifications coming within the scope and spirit of the invention.

It is claimed:

1. The process of refining" a crude petroleum oil which comprises subjecting it to continuous counter-current extraction with a solution consisting of an alkylol amine dissolved in a low molecular weight water-soluble oxygen-containing organic solvent to remove naphthenic acids substantially completely from said crude oil, whereby said crude oil is made substantially acidfree and substantially,non-corrosive during storage and subsequent distillation and refining treatments, separating the solvent extract now comprising solvent and dissolved therein allqlol amine salts of naphthenic acids together with any unreacted alkylolamine, treating said solvent extract with carbon dioxide to convert said alkylolamine naphthenates into corresponding alkylolamine-carbonates and liberate free naphsesame thenic acids which are insoluble in the solvent solution of alkylolamine and carbonates thereof. separating said liberated naphthenic acids from said solvent solution containing alkylolaminecarbonates and heating said solution to drive off carbon dioxide from said carbonates, thereby regenerating alkylolamine in solvent solution, and finally recycling said alkylolamine in solvent solution.

2. Process according to claim 1 in which the solvent is a lower aliphatic alcohol.

a 3. Process according to claim 1 in which the alkylol amine contains 1 to 3 ethanol. groups.

4. Process according to claim 1 in which the solvent is selected from the group consisting of isopropyl and ethyl alcohol and constitutes about 2% to 40% by volume based on the oil being treated.

5. Process according to claim 1 in which the extraction is carried out at a temperature between F. and the decomposition temperature of the amine soap of the naphthenic acids.

6. The continuous process of refining crude petroleum' oil which comprises subjecting said oil prior to any distillation or other refining treatment to a continuous countercurrent extraction with about 20% by volume of isopropyl alcohol and 3% by volume of mono-ethanol amine dissolved in said alcohol, whereby the naphthenic acids present in said'crude oil are substantially completely removed therefrom and converted into corresponding naphthenate salts of monoethanol amine dissolved in isopropyl alcohol, separating the resultant acid-free crude oil from the resultant solvent extract, treating the latter with carbon dioxide to convert the ethanol amine naphthenates into ethanol amine carbonate and thereby liberate free naphthenic acids as a liquid phase insoluble in the isopropyl alcohol solution containing ethanol amine carbonate, separating said liberated naphthenic acids in a substantially pure form available for commercial use and heating said isopropyl alcohol solution containing ethanol amine,carbonate to drive ofl. carbon dioxide and regenerate ethanol amine in solution in isopropyl alcohol, and recycling said solvent solution for use in further continuous solvent extraction of fresh crude oil.

7. In a process of refining a petroleum oil containing naphthenic acids, the steps which comprise contacting the oil with a solution consisting of a low molecular weight water-soluble oxygencontaining organic solvent having dissolved therein an organic water-soluble and alcoholsoluble amine that reacts with 'the naphthenic acids to form naphthenates thereof, and separatsaid organic salts without decomposing the liberated organic acids, and recovering thus liberated organic acids from the acid-treated solution.

9. Process according to claim 7, in which the contacting of said oil with the amine in the presence of the oxygen-containing solvent is carried out in a vertically-elongated extraction zone by continuous countercurrent extraction, the oil being fed continuously into a lower portion of the reaction zone and a solution'of the amine in the solvent being fed continuously into anupper portion of the extraction zone, while oil freed of organic acids is removed, continuously at the top of the extraction zone and the resultant solution of the organic salts in the organic solvent is removed continuously at the bottom of the extraction zone.

10. Process according to claim 7 in which the petroleum oil is a crude oil containing organic acids including naphthenic acids.

11. Process according to claim '1 in which the amine is an alkylol amine and the mutual solvent is a lower aliphatic alcohol that is water-soluble.

12. In the process of refining petroleum oil containing organic acid, the steps which consist in contacting the oil with an aliphatic watersoluble and alcohol-soluble amine having basic properties to form an organic salt thereof with the organic acid in the presence of a low molecular weight water-soluble oxygen-containing mutual organic solvent for the amine, the organic salt and carbonate salt of the amine, separating aresulting solution of the organic salt in said solvent from the oil, treating the separated solution ing from the oil resulting naphthenates andunreacted organic amine dissolved in the organic solvent which remains undissolved in the oil to leave the oil freed of naphthenic acids.

8. Process according to claim 7, followed by treating the separated resultant solution with carbon dioxide which liberates organic acids from with carbon dioxide to liberate organic acid from said salt and to convert the amine to'a carbonate salt, separating the liberated organic acid from the thus-treated solution of the carbonate salt in the solvent, heating the solution of the carbonate salt to decompose said carbonate salt and drive of! carbon dioxide gas whereby the amine is regenerated and reusing the regenerated amine in solution in the solvent in refining petroleum oil.

MACK C. FUQUA.. JOHN B. LOVELL.

REFERENCES CITED The following references are of record in the file of'this patent:

UNITED sra'rn's PATENTS Great Britain Jan. 27, 1939 

